Vehicle systems may include various vacuum consumption devices that are actuated using vacuum. These may include, for example, a brake booster and a purge canister. Vacuum used by these devices may be provided by a dedicated vacuum pump. In other embodiments, one or more aspirators (alternatively referred to as ejectors, venturi pumps, jet pumps, and eductors) may be coupled in the engine system that may harness engine airflow and use it to generate vacuum.
In yet another example embodiment shown by Bergbauer et al. in U.S. Pat. No. 8,261,716, a control bore is located in the wall of the intake such that when the throttle plate is at idle position, vacuum generated at the periphery of the throttle is used for a vacuum consumption device. Therein, the positioning of the throttle plate in an idle position provides a constriction at the throttle plate's periphery. The increasing flow of intake air through the constriction results in a venturi effect that generates a partial vacuum. The control bore is sited so as to utilize the partial vacuum for a vacuum consumption device.
The inventors herein have identified potential issues with the above approach. As an example, the vacuum generation potential of the throttle is limited. For example, a single control bore at one location in the intake, as shown in U.S. Pat. No. 8,261,716, is utilized by the vacuum consumption device even though vacuum may be generated at the entire periphery of the throttle. To use vacuum generated at the entire periphery of the throttle, more control bores may be needed in the intake passage. However, fabricating these control bores may result in significant modifications to the design of the intake passage which can increase related expenses.
In the approaches that use one or more aspirators to generate vacuum, additional expenses may be incurred because of individual parts that form the aspirator including nozzles, mixing and diffusion sections, and check valves. Further, at idle or low load conditions, it may be difficult to control the total air flow rate into the intake manifold since the flow rate is a combination of leakage flow from the throttle and airflow from the aspirator. Typically, an aspirator shut off valve (ASOV) may be included along with the aspirator to control airflow but with added cost. Further, installing aspirators in the intake can lead to constraints on space availability as well as packaging issues.
The inventors herein have identified an approach to at least partly address the above issues. In one example approach, a method is provided for an engine including a hollow intake throttle plate having a perforated edge. The method comprises adjusting a position of the hollow throttle plate with the perforated edge and generating vacuum via intake airflow past the perforated edge of the hollow throttle plate. The generated vacuum is then applied to a vacuum consumption device fluidly coupled to the hollow throttle plate via a hollow shaft. In this way, the throttle plate can function as an aspirator and supply vacuum to the vacuum consumption device.
As an example, an engine intake throttle may be configured as a hollow throttle plate mounted on a hollow shaft. The hollow shaft may fluidically couple the hollow space within the throttle plate to a vacuum consumption device. The throttle plate may further include a plurality of perforations around the periphery of the plate. The perforations may be dispersed uniformly or may be aggregated in specific locations along the edge of the throttle plate. When the vacuum demand of the vacuum consumption device coupled to the hollow throttle plate increases, the throttle plate may be adjusted to a more closed position. As a result, vacuum may be generated by the flow of intake air through a constriction created between the inside edge of the intake passage and the periphery of the throttle. This vacuum may be applied to the vacuum consumption device by flowing air from the vacuum consumption device through the hollow shaft into the hollow throttle plate and thereon, into intake airflow through the perforations at the edge of the hollow throttle plate. Once sufficient vacuum has been generated, the throttle position may be returned to a more open position.
In this way, a venturi flow passage created at the boundary of the hollow throttle plate in a more closed position can be advantageously used to generate vacuum for a vacuum consumption device. Perforations at the periphery of the throttle plate can be used to provide a channel to draw air or gas from the vacuum consumption device via the hollow shaft. By adjusting the location and size of perforations along the throttle periphery, vacuum can be generated over a larger portion of the throttle's periphery, such as over the entire periphery. As such, this improves the vacuum generation potential of the throttle plate. In addition, airflow into the intake manifold can be better controlled by adjusting the distance between the inside of the intake passage and the edge of the throttle plate. Furthermore, since air received from the vacuum consumption device during vacuum application is received substantially at the throttle plate, airflow errors can be better compensated for. By combining the functions of a throttle and an aspirator into a single hollow throttle plate with a perforated edge and a hollow shaft, additional control valves, such as an ASOV, and parts may not be needed. Further, the vacuum generation ability of the throttle is improved without requiring significant modifications to the intake passage. By reducing the number and size of components required for vacuum generation, manufacturing expenses may be lowered and packaging issues may be averted.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.